The present invention relates to diagnostic imaging methods and systems. In particular, the present invention relates to methods and systems for device-less gating of a stream of sinogram data.
At least some known Positron Emission Tomography (PET) and Computed Tomography (CT) systems experience image quality that is highly affected by physiological patient motion. Such image quality may affect the diagnosis. Lung nodules, cardiac wall features or other small features of interest that move due to physiological motion such as cardiac and respiratory motion, may appear unfocused or faint without proper corrections. By employing a cardiac and/or respiratory gating protocol during scan acquisition, images may be classified according to physiologic position in the cardiac/respiratory cycle. The gating technique may correct for motion artifacts in images. Also, the image pathway of the nodule or other features of interest may be tracked.
Respiratory gating can be accomplished through the use of many different devices, which detect chest wall motion, such as spirometers, bellows, ultrasonic devices, and external infrared camera systems. Setup and calibration of the devices and systems for monitoring physiological movement can be long and complicated, and is not typically used for all exams. Furthermore, when gating on different systems and/or at different times, errors may be introduced when attempting to plan therapy dynamically. However, without the detection of and correction for physiological motion, incorrect diagnoses may result.